Tuberculosis (TB) is an infectious disease usually caused by the bacterium Mycobacterium tuberculosis (MTB). Tuberculosis generally affects the lungs, but can also affect other parts of the body. Most infections do not have symptoms, in which case it is known as latent tuberculosis. About 10% of latent infections progress to active disease which, if left untreated, kills about half of those infected. The classic symptoms of active TB are a chronic cough with blood-containing sputum, fever, night sweats, and weight loss. It was historically called “consumption” due to the weight loss. Infection of other organs can cause a wide range of symptoms. Tuberculosis is spread through the air when people who have active TB in their lungs cough, spit, speak, or sneeze. People with latent TB do not spread the disease. Active infection occurs more often in people with HIV/AIDS and in those who smoke. Diagnosis of active TB is based on chest X-rays, as well as microscopic examination and culture of body fluids. Diagnosis of latent TB relies on the tuberculin skin test (TST) or blood tests.
Prevention of TB involves screening those at high risk, early detection and treatment of cases, and vaccination with the bacillus Calmette-Guérin (BCG) vaccine. Those at high risk include household, workplace, and social contacts of people with active TB. Treatment requires the use of multiple antibiotics over a long period of time. Antibiotic resistance is a growing problem with increasing rates of multiple drug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB).Presently, one-quarter of the world’s population is thought to be infected with TB. New infections occur in about 1% of the population each year. In 2016, there were more than 10 million cases of active TB which resulted in 1.3 million deaths. This makes it the number one cause of death from an infectious disease. More than 95% of deaths occurred in developing countries, and more than 50% in India, China, Indonesia, Pakistan, and the Philippines. The number of new cases each year has decreased since 2000. About 80% of people in many Asian and African countries test positive while 5–10% of people in the United States population test positive by the tuberculin test. Tuberculosis has been present in humans since ancient times World Health Organization. (2002).
Types of tuberculosis
Tuberculosis (TB) may be regarded in three categories: active disease, latent infection and Miliary tuberculosis. The most common form of active TB is lung disease, but it may invade other organs, so-called “extrapulmonary TB.”
Active TB Disease
Active TB is an illness in which the TB bacteria are rapidly multiplying and invading different organs of the body. The typical symptoms of active TB variably include cough, phlegm, chest pain, weakness, weight loss, fever, chills and sweating at night. A person with active pulmonary TB disease may spread TB to others by airborne transmission of infectious particles coughed into the air.
If you are diagnosed with an active TB disease, be prepared to give a careful, detailed history of every person with whom you have had contact. Since the active form may be contagious, these people will need to be tested, as well.
Multi-drug treatment is employed to treat active TB disease. Depending on state or local public health regulations, you may be asked to take your antibiotics under the supervision of your physician or other healthcare professional. This program is called “Directly Observed Therapy” and is designed to prevent abandonment or erratic treatment, which may result in “failure” with continued risk of transmission or acquired resistance of the bacteria to the medications, including the infamous multi-drug resistant TB (MDR-TB).
Latent TB Infection
Many of those who are infected with TB do not develop overt disease. They have no symptoms and their chest x-ray may be normal. The only manifestation of this encounter may be reaction to the tuberculin skin test (TST) or interferon-gamma release assay (IGRA). However, there is an ongoing risk that the latent infection may escalate to active disease. The risk is increased by other illnesses such as HIV or medications which compromise the immune system. To protect against this, the United States employs a strategy of preventive therapy or treatment of latent TB infection.
Miliary TB is a rare form of active disease that occurs when TB bacteria find their way into the bloodstream. In this form, the bacteria quickly spread all over the body in tiny nodules and affect multiple organs at once. This form of TB can be rapidly fatal. World Health Organization. (2002).
Causes of Tuberculosis
Tuberculosis (TB) is caused by a type of bacterium called Mycobacterium tuberculosis. It spread when a person with active TB disease in their lungs coughs or sneezes and someone else inhales the expelled droplets, which contain TB bacteria (Schiffman, 2009).
Signs and Symptoms
Tuberculosis may infect any part of the body, but most commonly occurs in the lungs (known as pulmonary tuberculosis).Extrapulmonary TB occurs when tuberculosis develops outside of the lungs, although extrapulmonary TB may coexist with pulmonary TB.
General signs and symptoms include;
- Cough lasting more than two to three weeks
- Coughing up sputum (phlegm) or blood
- Unexplained weight loss
- Fever or chills
- Night sweats
- Fatigue (unusual tiredness)
- Loss of appetite and chest pain. (Schiffman, 2009).
Anyone can become infected with Mycobacterium tuberculosis simply by breathing in the germs; one can be at risk of TB infection if you are around people with active TB disease who are coughing, which releases bacteria into the air. The risk of infection increases for intravenous drug users, healthcare workers, and people who live or work in a homeless shelter, migrant farm camp, prison or jail, or nursing home.
Most people who are infected with the bacteria that cause TB do not develop active disease. The following factors increase the risk that latent disease will develop into active disease:
- Infection with HIV, the virus that causes AIDS and weakens the immune system
- Diabetes mellitus
- Low body weight
- Head or neck cancer, leukemia, or Hodgkin’s disease
- Some medical treatments, including corticosteroids or certain medications used for autoimmune or vasculitic diseases such as rheumatoid arthritis or lupus, which suppress the immune system.
- Silicosis, a respiratory condition caused by inhaling silica dust.
Mode of Transmission
When people with active pulmonary TB cough, sneeze, speak, sing, or spit, they expel infectious aerosol droplets 0.5 to 5.0 µm in diameter. A single sneeze can release up to 40,000 droplets. Each one of these droplets may transmit the disease, since the infectious dose of tuberculosis is very small (the inhalation of fewer than 10 bacteria may cause an infection). People with prolonged, frequent, or close contact with people with TB are at particularly high risk of becoming infected, with an estimated 22% infection rate. A person with active but untreated tuberculosis may infect 10–15 (or more) other people per year. Transmission should occur from only people with active TB – those with latent infection are not thought to be contagious. The probability of transmission from one person to another depends upon several factors, including the number of infectious droplets expelled by the carrier, the effectiveness of ventilation, the duration of exposure, the virulence of the M. tuberculosis strain, the level of immunity in the uninfected person, and others. The cascade of person-to-person spread can be circumvented by segregating those with active (“overt”) TB and putting them on anti-TB drug regimens. After about two weeks of effective treatment, subjects with nonresistant active infections generally do not remain contagious to others. If someone does become infected, it typically takes three to four weeks before the newly infected person becomes infectious enough to transmit the disease to others.
About 90% of those infected with M. tuberculosis have asymptomatic, latent TB infections (sometimes called LTBI), with only a 10% lifetime chance that the latent infection will progress to overt, active tuberculosis disease. In those with HIV, the risk of developing active TB increases to nearly 10% a year. If effective treatment is not given, the death rate for active TB cases is up to 66%.TB infection begins when the mycobacteria reach the alveolar air sacs of the lungs, where they invade and replicate within endosomes of alveolar macrophages. Macrophages identify the bacterium as foreign and attempt to eliminate it by phagocytosis. During this process, the bacterium is enveloped by the macrophage and stored temporarily in a membrane-bound vesicle called a phagosome. The phagosome then combines with a lysosome to create a phagolysosome. In the phagolysosome, the cell attempts to use reactive oxygen species and acid to kill the bacterium. However, M. tuberculosishas a thick, waxy mycolic acid capsule that protects it from these toxic substances. M. tuberculosis is able to reproduce inside the macrophage and will eventually kill the immune cell. The primary site of infection in the lungs, known as the “Ghon focus”, is generally located in either the upper part of the lower lobe, or the lower part of the upper lobe. Tuberculosis of the lungs may also occur via infection from the blood stream. This is known as a Simon focus and is typically found in the top of the lung. This hematogenous transmission can also spread infection to more distant sites, such as peripheral lymph nodes, the kidneys, the brain, and the bones. All parts of the body can be affected by the disease, though for unknown reasons it rarely affects the heart, skeletal muscles, pancreas, or thyroid.
To diagnose tuberculosis (TB), your health care provider will gather five important pieces of information during the complete history and physical examination:
- History of exposure
- Tuberculin skin test or blood test for TB
- Chest X-ray or chest CT scan
- Sputum test
You should be tested for TB if:
- You think you might have active TB disease.
- You have spent time with a person you know or suspect has active TB disease.
- You are infected with HIV or have another condition that puts you at high risk for active TB disease.
- You are from a country where active TB disease is very common (most countries in Latin America, the Caribbean, Africa, and Asia and Eastern Europe and Russia).
- You live or work somewhere where active TB disease is more common, such as a homeless shelter, migrant farm camp, prison or jail, or some nursing homes.
- You use illegal intravenous drugs.
History of Exposure
Getting an accurate history is important in diagnosing and treating TB. Like any disease, early intervention and treatment is very important.
Tuberculin Skin Test
The tuberculin skin test (or PPD) uses an extract of killed TB germs. The killed germs are injected into the skin. If a person has been infected with TB, a lump will form at the site of the injection. This is a positive test. This often means that TB germs have infected the body. It does not often mean the person has active disease. People with positive skin tests but without active disease cannot transmit the infection to others.
Tuberculosis Blood Test
There are two new blood tests that have recently been developed to test for exposure to tuberculosis germs. They are still used in research settings, but some hospitals and clinics are using them in place of the tuberculin skin test. Each tests involves collection of blood that is then stimulated with a group of antigens (proteins) found in the bacteria that causes TB. If your immune system has ever seen these antigens, your cells will produce interferon-gamma, a substance produced by our immune system and, which can be measured in a laboratory. There are two tests available, the Quantiferon-TB® Gold (QFT) Test and the T-Spot®.TB Test. These tests appear to be more sensitive and specific than the tuberculin skin test. Importantly, unlike the tuberculin skin tests, they are not affected by previous BCG vaccination.
If a person has been infected with TB, but active disease has not developed, the chest X-ray will often be normal. Most people with a positive PPD (skin test) or TB blood test have normal chest X-rays and continue to be healthy. For such people, preventive medication may be recommended.
However, if the germ has attacked and caused inflammation in the lungs, an abnormal shadow may be visible on the chest X-rays. For these people, diagnostic tests (sputum tests) and treatment often are appropriate.
Samples of sputum coughed up from the lungs can be tested to see if TB germs are present. The sputum is examined under a microscope (a “sputum smear”) to look for evidence of the TB organisms. Southwick F (2007).
Prevention of Tuberculosis
Tuberculosis prevention and control efforts rely primarily on the vaccination of infants and the detection and appropriate treatment of active cases. The World Health Organization has achieved some success with improved treatment regimens, and a small decrease in case numbers. The US Preventive Services Task Force (USPSTF) recommends screening people who are at high risk for latent tuberculosis with either tuberculin skin tests or interferon-gamma release assays.Harris (2013).
It is the most widely used vaccine worldwide, with more than 90% of all children being vaccinated. The immunity it induces decreases after about ten years. As tuberculosis is uncommon in most of Canada, the United Kingdom, and the United States, BCG is administered to only those people at high risk. Part of the reasoning against the use of the vaccine is that it makes the tuberculin skin test falsely positive, reducing the test’s usefulness as a screening tool. A number of new vaccines are currently in development.Hawn (2014).
Treatment of Active Disease
Treatment of active TB requires combination therapy. The usual regimen is:
- Isoniazid (INH)
- Rifampin (also known as rifampicin, Rifadin, or Rimactane)
- Ethambutol (Myambutol)
These four drugs are taken daily for two months. Tests can be done to see how well the drugs are fighting the TB. If the drugs are fighting the TB well, then the treatment changes to just two drugs: isoniazid plus rifampin for four more months. Sometimes the treatment will last longer, depending on whether or not the TB is resistant to these drugs, or if the TB disease has spread through the bloodstream to other parts of the body.
Some TB drugs can interact with HIV drugs. Rifampin, for example, can interfere with protease inhibitors and non-nucleoside reverse transcriptase inhibitors. This can make it difficult to treat both diseases at the same time. If you are taking a protease inhibitor, your health care provider may make changes to your TB drugs. Your provider may also adjust your drug doses when you are being treated for both TB and HIV. Some people living with HIV may need longer TB treatment than people without HIV.
As with HIV, taking your TB drugs exactly as prescribed (good adherence) is very important. Even though symptoms usually improve after three to four weeks and you feel better before you have finished taking all your drugs, the full course of treatment must be completed. This helps prevent TB from coming back and becoming resistant to drugs.
- Leafy, dark-colored greens like kale and spinach
- Antioxidant-rich, brightly-colored vegetables, such as carrots, peppers, and squash, and fruits, like tomatoes, blueberries, and cherries.
- Egg, fish, and cottage Cheese.
- Skimmed milk and yoghurt.
- There is serious need for increased level of physical activities.
Food to Avoid
- Limit refined products, like sugar, white breads, and white rice.
- Abstain from food items with high fat and high cholesterol levels.
- Abstain from Red meat.
- Drink less of the caffeinated drinks like coffee, cold drinks as well as energy drinks.
- Don’t chew or smoke tobacco,
Tuberculosis infection and disease remain common in populations characterized by poor housing conditions, drug use, and HIV infection. Linking a major medical provider with community-based organizations is an effective means to provide highly targeted screening services to a population at serious risk for disease acquisition and transmission.
Ferri, F. (2010). “Diagnosis of tuberculosis” a practical guide to the differential diagnosis of symptoms, signs, and clinical disorders (2nd ed.). Philadelphia, PA: Elsevier/Mosby. p. Chapter T. ISBN 978-0323076999.
Harris, .R. E. (2013). “Prevention and treatment of tuberculosis”. Burlington, p. 682. ISBN 9780763780470.
Hawn TR, Day TA, Scriba TJ, Hatherill M, Hanekom WA, Evans TG, Churchyard GJ, Kublin JG, Bekker LG, Self SG (2014). “Tuberculosis vaccines and prevention of infection”. Microbiology and Molecular Biology Reviews. 78 (4): 650–71. PMC 4248657. PMID 25428938.
Schiffman, G ( 2009). “Tuberculosis Symptoms and causes”. Medicine Health. Archived from the original on 16 May 2009.
Southwick F (2007). “Chapter 4: “diagnosis of tuberculosis”. Infectious Diseases: A Clinical Short Course, 2nd ed. McGraw-Hill Medical Publishing Division. pp. 104, 313–4. ISBN 978-0-07-147722-2.
World Health Organization. (2002).”Tuberculosis and types of tuberculosis“. Archived from the original on 17 June 2013.